Multidimensional IR Study Of The Structure And Dynamics Of Elastin Protein

Abstract

Elastin protein is responsible for the elasticity of organs including the skin, lungs, and arterial tissues. Upon heating to physiological temperature the elastic region undergoes an inverse temperature transition (ITT) from an extended to a folded state. It is hypothesized that the ITT results from changes in water structure around the elastic regions hydrophobic side chains. To investigate this hypothesis we have performed temperature dependent FTIR and 2D IR experiments on the amide I, amide A, and water OH stretching vibrations of bovine neck elastin and synthetic peptide mimics. FTIR spectra of hydrated films in the OH stretch region show spectral signatures which are indicative of water molecules interacting with the protein. This spectral signature displays a large absorption band centered at 3450cm-1, extending as far as 3600cm-1. This band is suggestive of weakly hydrogen bound water and may be an indicator of hydrophobic hydration. In 2D IR experiments we have observed a vibrational coupling between the high frequency water band and absorption bands at lower frequency that correspond to the amide A vibration of the protein backbone. Vibrational coupling between these modes may be an indicator of water molecules located at the protein water interface. Finally, 2D IR spectra on the amide 1 vibration of the protein backbone display a cross peak between a well resolved proline vibration centered at 1610cm-1 that originates from the elastic region of the protein, and a vibration centered at 1675cm-1 whose associated secondary structure is currently undetermined. From this data we hope to determine water's role in the ITT and propose a secondary structure for the elastic region of the protein.